Your description of the issue is not entirely clear.
If this is your issue:
There is a series of values in cells in column C (for this example I put data into cells C2 to C14)
and you have a cell in column B containing a value (I used cell B2)
then you want cell B2 to be Red when the value in B2 matches one of the values in cells C2 to C14
Select cell B2
From the menu select Format - Conditional Formatting ...
In the 'Condition 1' drop-down select 'Formula Is'
In the formula box enter this:
Click the 'Format...' button and select a red color in the 'Patterns' Tab
Click OK and OK
Now when the value in B2 matches one of the values in C2 to C14 the cell color will be Red
The conditional formatting formula works like this:
VLOOKUP looks for the value in B2 in the range C2 to C14, as this is a single column range, and we don't need it to return anything else, the column offset is set to 1. FALSE in VLOOKUP ensures that it only returns a value if there is an exact match.
If it does not find an exact match it returns the NA error
The IF function tests VLOOKUP for the error value using ISNA
If VLOOKUP doesn't find a match it returns the NA error and ISNA is therefore TRUE
The structure of the IF function is IF(test, value if True, value if False)
In this case if the test is true i.e. VLOOKUP returned the NA error, IF returns FALSE
If a match was found, VLOOKUP does not return the NA error and the IF ISNA is false and IF returns TRUE
The conditional formatting is applied if the final outcome of the formula is TRUE, in this case when there is a match.
If you copy cell B2 to B3 then B3 will also have the same conditional formatting, but this time B3 is compared to the values in C2 to C14
If your requirements are different, please include all the details - please be specific about cells (compared to Column C means compared to cells C1 to C65536) and be specific about what is being compared to what (all of Column B compared to Column C does this mean B1 compared to C1, all the way down to B65536 compared to C65536)